Soy intake may slash heart disease risk by 12%, but only for equol producers

By Stephen Daniells

- Last updated on GMT

Image: iStockPhoto
Image: iStockPhoto

Related tags Randomized controlled trial Heart Clinical trial Epidemiology

Soy supplements may reduce the risk of cardiovascular risk for people able to produce equol, a microbial-derived metabolite of the isoflavone daidzein, but equol supplements themselves may not have the same effects, says a new study.

Individuals have different abilities to produce equol – an isoflavandiol that may have beneficial effects on prostate health, bone health, heart health, and for managing menopausal symptoms. Equol is produced in the gut by bacteria, but only 30 to 50% of people are reported to have the intestinal bacteria necessary to produce it.

Results of a double-blind randomized controlled trial published in the American Journal of Clinical Nutrition​, indicated that isoflavone supplementation in people with the equol producer (EP) phenotype was associated with a improvements in arterial stiffness, which could equate to an 11-12% reduced risk of cardiovascular disease.  

However, supplementing non-equol producers with equol did not produce the same cardiovascular benefits, said researchers from the University of East Anglia in England.

“In one of the first randomized controlled isoflavone trials to prospectively recruit EPs to our knowledge, we observed acute improvements in [carotid-femoral pulse-wave velocity (cfPWV)] after soy isoflavone intakes at a dose readily achieved through the habitual diet and provide evidence of the potential significant importance of the EP phenotype,” ​they wrote.  

“The potential clinical importance of this finding is noteworthy given that cfPWV, a measure of arterial stiffness, has been recently identified within the highest category of surrogate markers of clinical endpoints and was previously identified as an independent predictor of vascular clinical outcomes.”

Study details

Led by Professor Aedin Cassidy, the researcgers recruited 14 equol producers and 14 non-equol producers to participate in their study. Participants were randomly assigned to receive either soy isoflavone supplements (80-mg aglycone equivalents of daidzein and genistein, SoyLife, Frutarom) or placebo and their cfPWV were measure at time zero, and again after six and 24 hours.

Results of this study showed that plasma equol concentrations increased significantly in the equol producers, and this was associated with significant improvements in cfPWV 24 hours post-consumption, but not after 6 hours.

On the other hand, no effects were observed in the non-equol producers at any time.

intestines gut Ben-Schonewille
Only 30 to 50% of people are reported to have the intestinal bacteria necessary to produce equol. Image © iStockPhoto / Ben-Schonewille

In another experiment, the non-equol producers received 40 mg of a commercially available S-(–)equol supplement (Otsuka Pharmaceutical) and vascular measurements were taken two hours after intake. “We chose a 40-mg dose of S-equol, because it was previously shown to be bioavailable and was considered likely to attain plasma concentrations a priori in men,” ​they explained.

While plasma equol levels did increase in these participants, no improvements in cfPWV were observed.

“These findings imply that, at least in the acute setting, the EP phenotype is a necessity to unlock the vascular benefits of elevated equol concentrations,” ​wrote the researchers. “These findings are generally consistent with a previous 12-wk intervention with SE5-OH​ in which male Eps and non-EPs experienced no significant vascular improvements; however, in the same study, female postmenopausal nonEPs significantly reduced cardio-ankle vascular index (CAVI, a measure of aortic stiffness) after consumption of 10 mg S-(–) equol/d (21), suggesting potential differential effects by sex.”

“Further data from long-term clinical trials that prospectively recruit EPs are required to confirm whether the acute improvements in cfPWV (which would equate to an 11–12% risk reduction for CVD) are sustained and of long-term clinical relevance.”

Source: American Journal of Clinical Nutrition
Published online ahead of print, doi:
“Acute benefits of the microbial-derived isoflavone metabolite equol on arterial stiffness in men prospectively recruited according to equol producer phenotype: a double-blind randomized controlled trial”
Authors: S. Hazim et al. 

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